What makes SAP HANA fundamentally different?
SAP HANA is different by design. It stores all data in-memory, in columnar format and compressed. Because HANA is so fast, sums, indexes, materialized views and aggregates are not required, and this can reduce the database footprint by 95%. Everything is calculated on-demand, on the fly, in main memory. This makes it possible for companies to run OLTP and analytics applications on the same instance at the same time, and to allow for any type of real-time, ad hoc queries and analyses.
On top of this SAP built solutions to all the problems of columnar databases, like concurrency (HANA uses MVCC) and row-level insert and update performance (HANA uses various mechanisms like a delta store).
If this wasn’t enough SAP added a bunch of engines inside HANA to provide virtual OLAP functionality, data virtualization, text analysis, search, geospatial, graph (will be available soon) and web. It supports open standards like REST, JSON, ODBO, MDX, ODBC and JDBC. There is as much functionality in there as a whole Oracle or IBM software stack, in one database.